Synthesis: Thresholds in conservation and management

This paper is a brief overview of some of the key issues which have emerged from the preceding set of papers on ecological thresholds. These include:

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Whether threshold relationships are common and widespread.

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The potential for large variations in the use and application of the threshold concept to lead to adverse conservation outcomes, particularly when overly simplistic levels of vegetation cover are specified by policy makers and land managers.

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The inherent multi-variate nature of landscape processes and responses of individual species and assemblages that creates variability in datasets. This may lead to a limited ability to make accurate predictions from threshold relationships, even when those relationships are highly statistically significant.

We believe that although the threshold concept is an appealing one and there is some empirical evidence to support it in some landscapes, it is not free of problems and a concerted research effort on the topic is needed. This is particularly important if it is to have value for robustly underpinning applied landscape management practices without unintentionally having negative impacts on rates of species loss or the loss of particular species.     

Small mammals, habitat patches and PVA models: a field test of model predictive ability

The results are described of comparisons between actual values for patch occupancy for two species of Australian small mammals (Bush Rat Rattus fuscipes and Agile Antechinus Antechinus agilis) determined from field sampling and predictions of patch occupancy made using VORTEX, a generic simulation model for Population Viability Analysis (PVA). The work focussed on a fragmented forest in south-eastern Australia comprised of a network of 39 patches of native eucalypt forest surrounded by extensive stands of exotic softwood Radiata Pine (Pinus radiata) plantation. A range of modelling scenarios were completed in which four broad factors were varied: (1) inter-patch variation in habitat quality; (2) the pattern of inter-patch dispersal; (3) the rate of inter-patch dispersal; and (4) the population sink effects of the Radiata Pine matrix that surrounded the eucalypt patches. Model predictions were made for the total number of animals, the distribution of animal density among patches, the total number of occupied patches, and the probability of patch occupancy. Predictions were then compared with observed values for these same measures based on extensive field surveys of small mammals in the patch system. For most models for the Bush Rat, the predicted relative density of animals per patch correlated well with the values estimated from field surveys. Predictions of patch occupancy were not significantly different from the actual value for the number of occupied patches in half the models tested. The better models explained 10-16% of the log-likelihood of the probability of patch occupancy. While some of the models gave reasonable forecasts of the number of occupied patches, even in these cases, they had only moderate ability to predict which patches were occupied. Field surveys revealed there was no relationship between patch area and population density for the Agile Antechinus—an outcome correctly predicted by only a few models. Five of the 18 scenarios completed for the Agile Antechinus gave predicted numbers of occupied patches not significantly different from the observed number. In each of these five cases, large standard deviations around the mean predicted value meant uncertainty generated by the simulation model limited the predictive power of the PVA. Some of the models gave reasonable predictions for the number of occupied patches, but those models were unable to predict which ones were actually occupied. The results of our study suggest that key processes influencing which specific patches would be occupied were not modelled appropriately. High levels of variability and fecundity drive the population dynamics of the Bush Rat and Agile Antechinus, making the patch system unpredictable and difficult to model accurately. Despite the fact that both the Bush Rat and the Agile Antechinus are two of the most studied mammals in Australia, there are attributes of their biology that are presently poorly understood (which were not included in the VORTEX model), but which could strongly influence patch occupancy. For example, local landscape features may be important determinants of inter-patch movement and habitat utilisation in the patch system. Further empirical studies are needed to explore this aspect of small mammal biology.     

Use of anti-inflammatory and analgesic drugs in dogs and cats

SUMMARY: Responses (486) were collated from a survey of 5054 Australian veterinarians on their use of anti-inflammatory and analgesic drugs in dogs and cats. Almost all respondents used glucocorticoids (usually prednisolone) to treat allergic, pruritic dermatoses in dogs, while two-thirds also gave fatty acid supplements and one-half used antihistamines. Almost 60% of respondents initially injected a glucocorticoid (frequently a long-acting preparation) when treating inflammatory skin diseases in dogs. More than 90% of respondents used glucocorticoids to treat immunemediated haemolytic anaemia or thrombocytopenia, and about one-third also gave cytotoxic drugs. Administration of prednisolone on alternate days was generally favoured for long-term enteral steroid therapy. Phenylbutazone was the most preferred treatment for painful or inflammatory musculoskeletal disorders of dogs, but aspirin and pentosan polysulphate were also used widely. Regarding the use of analgesics drugs generally, both narcotic analgesics and non-steroidal anti-inflammatory drugs (NSAIDs) were used more widely in dogs than in cats, but alpha-2 agonists were used similarly in both species. The most commonly used narcotic analgesics were pethidine and buprenorphine in both species, while the NSAIDs used most often were flunixin and dipyrone in dogs and ketoprofen in cats. More than 80% of respondents generally used analgesic drugs with potentially painful surgical procedures, with doses given usually before anaesthetic recovery. Analgesic use rates varied with the condition, ranging from 94% for patients with acute severe trauma, through 60% for cruciate ligament repair and 29% for perineal herniorrhaphy, to about 5% for ovariohysterectomy and dog castration. The three clinical signs most frequently nominated as indicators of pain in dogs and cats were (in descending order) vocalisation, response to handling or palpating the affected area, and mental depression. Other items mentioned frequently were behavioural changes and immobility (in both species), inappetence/anorexia in cats, and altered respiration in dogs.     

Landscape,fire and habitat: which features of recently burned heathland influence site occupancy of an early successional specialist?

Context

Multiple ecological drivers generate spatial patterns in species’ distributions. Changes to natural disturbance regimes can place early successional habitat specialists at an increased risk of extinction by altering landscape patterns of habitat suitability.

Objectives

We developed a series of hypotheses to evaluate the effects of landscape structure, fire history, and site-level habitat quality on site occupancy by an early successional specialist, the eastern chestnut mouse (Pseudomys gracilicaudatus).

Methods

We obtained eight years of monitoring data from 26 sites in recently burned heathland in southeast Australia. We used generalised linear models to determine which explanatory variables were related to occupancy. We also explored predictability in patterns of small mammal species co-occurrence.

Results

Landscape structure (patch area, landscape heterogeneity) was strongly related to site occupancy. Site occupancy was associated with dead shrubs in the understory and rock cover on ground layer, but was not directly influenced by recent or historical fire. Contrary to contemporary ecological theory, we found no predictable species associations in our early successional community.

Conclusions

We recommend surveys take account of landscape configuration and proximity to suitable habitat for optimal results. Fire regimes expected to promote eastern chestnut mouse population growth should encourage the retention of critical habitat features rather than be based on temporal rates of successional stages. For management to adequately account for post-disturbance patterns in early successional communities, a species-by-species, multi-scaled approach to research is necessary.

     

A long-snouted predatory dinosaur from africa and the evolution of spinosaurids

Fossils discovered in Lower Cretaceous (Aptian) rocks in the Tenere Desert of central Niger provide new information about spinosaurids, a peculiar group of piscivorous theropod dinosaurs. The remains, which represent a new genus and species, reveal the extreme elongation and transverse compression of the spinosaurid snout. The postcranial bones include blade-shaped vertebral spines that form a low sail over the hips. Phylogenetic analysis suggests that the enlarged thumb claw and robust forelimb evolved during the Jurassic, before the elongated snout and other fish-eating adaptations in the skull. The close phylogenetic relationship between the new African spinosaurid and Baryonyx from Europe provides evidence of dispersal across the Tethys seaway during the Early Cretaceous.     

An approximately 15,000-year record of El Nino-driven alluviation in southwestern ecuador

Debris flows have deposited inorganic laminae in an alpine lake that is 75 kilometers east of the Pacific Ocean, in Ecuador. These storm-induced events were dated by radiocarbon, and the age of laminae that are less than 200 years old matches the historic record of El Nino events. From about 15,000 to about 7000 calendar years before the present, the periodicity of clastic deposition is greater than or equal to 15 years; thereafter, there is a progressive increase in frequency to periodicities of 2 to 8.5 years. This is the modern El Nino periodicity, which was established about 5000 calendar years before the present. This may reflect the onset of a steeper zonal sea surface temperature gradient, which was driven by enhanced trade winds.